JP5305923B2 - Radio communication base station apparatus and control channel MCS control method - Google Patents

Description

  The present invention relates to a radio communication base station apparatus and a control channel MCS control method.

  In recent years, in wireless communication, particularly mobile communication, various information such as images and data other than voice has been the object of transmission. In the future, it is expected that the demand for higher-speed transmission will increase further, and in order to perform high-speed transmission, wireless transmission technology that achieves high transmission efficiency by using limited frequency resources more efficiently is required. ing.

  One of the radio transmission technologies that can meet such demand is OFDM (Orthogonal Frequency Division Multiplexing). OFDM is a multicarrier transmission technology that transmits data in parallel using a large number of subcarriers, and has features such as high frequency utilization efficiency and reduced intersymbol interference in a multipath environment, and is effective in improving transmission efficiency. It is known.

  When this OFDM is used for a downlink and data for a plurality of radio communication mobile station apparatuses (hereinafter simply referred to as mobile stations) is frequency-multiplexed on a plurality of subcarriers, it is considered to perform frequency scheduling transmission.

  In frequency scheduling transmission, a radio communication base station apparatus (hereinafter simply referred to as a base station) allocates subcarriers adaptively to each mobile station based on reception quality for each frequency band at each mobile station. The multi-user diversity effect can be obtained. On the other hand, since frequency scheduling transmission is normally performed for each resource block obtained by blocking several adjacent subcarriers together, a very high frequency diversity effect cannot be obtained.

  In order to perform frequency scheduling transmission, the base station performs, for each subframe, a mobile station ID (user ID), a resource at the head of the subframe prior to data transmission, with respect to the data transmission destination mobile station in each subframe. Control information including a block number, a data channel modulation scheme, a coding rate (Modulation and Coding Scheme: MCS), and the like is transmitted. Further, this control information is transmitted by SCCH (Shared Control Channel). There are as many SCCHs as the number of mobile stations to which data is transmitted in the subframe, and the number of mobile stations per subframe is defined by, for example, a frequency bandwidth (hereinafter referred to as a system bandwidth) that can be used in a communication system. The That is, at the head of each subframe, the same number of SCCHs as the number of data channels in that subframe are multiplexed at the same time.

  SCCH is subjected to transmission power control for each mobile station. In this transmission power control, a plurality of SCCHs share power resources within the permissible transmission power (within the maximum transmission power) of the base station, the SCCHs for mobile stations near the cell boundary have high transmission power, and mobile stations in the cell center portion. SCCH is controlled to a low transmission power. By this transmission power control, it is possible to efficiently use limited power resources by interchanging between SCCHs for each mobile station.

On the other hand, in the standardization examination at this stage, the MCH of SCCH satisfies the coverage target of 95%, that is, 95% of all mobile stations existing in the cell can satisfy the required reception quality. It is said that it needs to be set to a proper MCS. For this reason, conventionally, the MCS of the SCCH is fixed to the MCS having a sufficiently low MCS level. For example, for SCCH, MCS with a modulation scheme of QPSK and a coding rate of R = 1/8 is set as a fixed MCS that satisfies a coverage target of 95% (see Non-Patent Document 1).
3GPP RAN WG1 Meeting document, R1-061278

  Thus, conventionally, since the MCS of the SCCH is fixed to the MCS having a sufficiently low MCS level, the amount of communication resources (time resource amount and frequency resource amount) consumed for the SCCH increases, and the SCCH The communication overhead due to increases. As a result, the data throughput decreases. Such an adverse effect due to the fact that the SCCS MCS is fixed to a sufficiently low MCS level MCS becomes larger as the number of multiplexed SCCHs, that is, the number of mobile stations per subframe increases.

  The objective of this invention is providing the MCS control method of the base station and control channel which can reduce the communication overhead by control channels, such as SCCH.

  The base station of the present invention is a base station device that multiplexes a plurality of control channels at the same time, an encoding unit that encodes the plurality of control channels, a modulation unit that modulates the plurality of control channels, A setting unit configured to set the MCS in the encoding unit and the modulation unit according to the number of multiplexed control channels.

  According to the present invention, communication overhead due to a control channel such as SCCH can be reduced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(Embodiment 1)
The configuration of base station 100 according to the present embodiment is shown in FIG. Base station 100 multiplexes a plurality of SCCHs at the same time.

  In base station 100, coding / modulating sections 101-1 to 101-n comprising SCCH coding section 11 and modulating section 12, and coding / modulating sections comprising data channel coding section 21 and modulating section 22 104-1 to 104-n and demodulation / decoding units 114-1 to 114-n including the demodulation unit 31 and the decoding unit 32 are provided by the number n of mobile stations with which the base station 100 can communicate. Also, the encoding / modulation units 101-1 to 101-n, the encoding / modulation units 104-1 to 104-n, and the demodulation / decoding units 114-1 to 114-n are respectively connected to the mobile stations 1 to n. Correspondingly provided.

  The MCS setting unit 120 sets the MCS in the encoding / modulation units 101-1 to 101-n. Details of the MCS setting in the MCS setting unit 120 will be described later.

  In the encoding / modulation sections 101-1 to 101-n, each encoding section 11 performs control information for each mobile station transmitted on the SCCH for each mobile station according to the MCS set by the MCS setting section 120. Encoding processing is performed, and each modulation unit 12 performs modulation processing on the encoded control information according to the MCS set by the MCS setting unit 120 and outputs the control information to the arrangement unit 102.

  Arrangement section 102 arranges control information for each mobile station on any of a plurality of subcarriers constituting an OFDM symbol, and outputs the information to transmission power control section 103. That is, arrangement section 102 arranges a plurality of SCCHs for each mobile station on any of a plurality of subcarriers constituting an OFDM symbol. By this arrangement processing in arrangement section 102, a plurality of SCCHs are frequency-multiplexed at the same time.

  Based on the reception quality information reported from each mobile station, transmission power control section 103 controls the transmission power of the control information within the allowable transmission power and outputs it to multiplexing section 106. At this time, the transmission power control unit 103 controls the transmission power of the control information for each SCCH based on the reception quality information of the entire communication band for each mobile station. Also, the SCCH transmission power of each mobile station is set to a transmission power at which each mobile station can receive control information with sufficient reception quality. More specifically, the transmission power control unit 103 increases the transmission power as the reception quality is lower, and decreases the transmission power as the reception quality is higher. As a result, the SCCH for the mobile station near the cell boundary is controlled to a high transmission power, and the SCCH for the mobile station near the cell center is controlled to a low transmission power. That is, transmission power control section 103 controls the transmission power of each of the plurality of SCCHs within the allowable transmission power according to the reception quality at each mobile station.

  In the encoding / modulation units 104-1 to 104-n, each encoding unit 21 performs encoding processing on transmission data for each mobile station, and each modulation unit 22 applies to transmission data after encoding. Then, modulation processing is performed and the result is output to the placement unit 105. The MCS at this time follows the MCS information input from the adaptive control unit 115.

  Arrangement section 105 arranges data for each mobile station in any of a plurality of subcarriers constituting an OFDM symbol and outputs the data to multiplexing section 106 in accordance with control from adaptive control section 115. At this time, arrangement section 105 arranges data for each mobile station on any of a plurality of subcarriers in units of resource blocks. The allocation unit 105 outputs the mobile station ID and the resource block number to the control information generation unit 116 as the allocation information of each data (information indicating which mobile station the data is allocated to which resource block).

  Multiplexing section 106 time-multiplexes the control information input from transmission power control section 103 on each data input from arrangement section 105 and outputs the result to IFFT (Inverse Fast Fourier Transform) section 107. Multiplexing of control information is performed for each subframe, for example, and control information is multiplexed at the head of each subframe.

  IFFT section 107 performs IFFT on a plurality of subcarriers on which control information is arranged or on a plurality of subcarriers on which data is arranged to generate OFDM symbols that are multicarrier signals. That is, IFFT section 107 generates an OFDM symbol in which a plurality of SCCHs are frequency-multiplexed or an OFDM symbol in which a plurality of data channels are frequency-multiplexed. Also, an OFDM symbol composed of SCCH and an OFDM symbol composed of a data channel are time-multiplexed in one subframe.

  CP (Cyclic Prefix) adding section 108 adds the same signal as the tail part of the OFDM symbol to the beginning of the OFDM symbol as a CP.

  Radio transmitting section 109 performs transmission processing such as D / A conversion, amplification and up-conversion on the OFDM symbol with the CP added, and transmits the result from antenna 110 to each mobile station.

  On the other hand, the radio reception unit 111 receives n OFDM symbols simultaneously transmitted from a maximum of n mobile stations via the antenna 110, and performs reception processing such as down-conversion and D / A conversion on these OFDM symbols. I do.

  CP removing section 112 removes the CP from the OFDM symbol after reception processing.

  An FFT (Fast Fourier Transform) unit 113 performs FFT on the OFDM symbol after CP removal, and obtains a signal for each mobile station multiplexed in the frequency domain. Here, each mobile station transmits a signal using different subcarriers or different resource blocks, and the signal for each mobile station includes reception quality information reported from each mobile station. . In each mobile station, reception quality is measured by reception SNR, reception SIR, reception SINR, reception CINR, reception power, interference power, bit error rate, throughput, MCS that can achieve a predetermined error rate, or the like. it can. The reception quality information may be expressed as CQI (Channel Quality Indicator), CSI (Channel State Information), or the like.

  In the demodulation / decoding units 114-1 to 114-n, each demodulation unit 31 performs demodulation processing on the signal after FFT, and each decoding unit 32 performs decoding processing on the demodulated signal. Thereby, reception data is obtained. Of the received data, reception quality information is input to transmission power control section 103 and adaptive control section 115.

  The adaptive control unit 115 performs adaptive control on transmission data to each mobile station based on reception quality information reported from each mobile station. That is, adaptive control section 115 selects MCS that can satisfy the required error rate and outputs MCS information to encoding / modulation sections 104-1 to 104-n based on the reception quality information. To do. This adaptive control is performed for each resource block. That is, the adaptive control unit 115 performs adaptive control of the data channel for each of a plurality of resource blocks. Also, the adaptive control unit 115 uses the scheduling algorithm such as the Max SIR method or the Proportional Fairness method to the placement unit 105 based on the reception quality information, and to which resource block the transmission data to each mobile station is assigned. Decide whether to place. Further, adaptive control section 115 outputs MCS information for each mobile station to control information generation section 116.

  The control information generation unit 116 generates control information for each mobile station, which includes arrangement information for each mobile station and MCS information for each mobile station, and outputs the control information to the corresponding encoding unit 11.

  Next, details of MCS setting in the MCS setting unit 120 will be described.

When the number of SCCH multiplexes, that is, when the number of mobile stations allocated per subframe is small (for example, when the number of multiplexes of SCCH is 2), the dispersion due to the small number of samples increases the dispersion There is a high probability that the mobile station exists in a certain range within the cell, and thus the probability that all mobile stations exist near the cell boundary is also high. Therefore, in this case, reception quality reported from each mobile station is also biased, and all reception quality is lowered. As a result, there is a higher probability that only SCCH with high transmission power is multiplexed. Also, the allowable transmission power in the base station is proportional to the number of multiplexed SCCHs, that is, the allowable transmission power decreases as the number of multiplexed SCCHs decreases. Therefore, if only the SCCH with high transmission power is multiplexed because the number of SCCH multiplexing is reduced, there is a possibility that the total SCCH transmission power may not be within the allowable transmission power. When the total SCCH transmission power does not fall within the allowable transmission power, transmission power control section 103 decreases the transmission power of each SCCH so that the total SCCH transmission power falls within the allowable transmission power. Therefore, in this case, the SCCH reception quality in each mobile station cannot satisfy the required reception quality. Further, since the number of mobile stations per subframe is small, if there are even a few mobile stations that cannot satisfy the required reception quality, the coverage target of 95% cannot be satisfied. Therefore, when the number of multiplexed SCCHs is small, it is necessary to compensate for a decrease in reception quality due to a decrease in transmission power with an increase in reception quality due to a decrease in MCS level. That is, when the SCCH multiplexing number is small, it is necessary to set the SCCS MCS to an MCS with a low MCS level.

  On the other hand, when the number of multiplexed SCCHs, that is, when the number of mobile stations allocated per subframe is sufficiently large (for example, when the number of multiplexed SCCHs is 12), the mobile stations are uniformly distributed in the cell. The probability of being distributed evenly is high. Therefore, in this case, the reception quality reported from each mobile station exists uniformly from high to low, and as a result, various transmissions from SCCH with high transmission power to SCCH with low transmission power are performed. The power SCCH is multiplexed. Further, as described above, the allowable transmission power in the base station is proportional to the SCCH multiplexing number, that is, the allowable transmission power increases as the SCCH multiplexing number increases. Therefore, in this case, the possibility that the total transmission power of SCCH falls within the allowable transmission power is sufficiently high. Therefore, when the SCCH multiplexing number is sufficiently large, the SCCH transmission power of all mobile stations can be set to a transmission power that satisfies the required reception quality. In addition, since the number of mobile stations per subframe is sufficiently large, even if there are some mobile stations that cannot satisfy the required reception quality, the 95% coverage target can be sufficiently satisfied. Therefore, when the number of multiplexed SCCHs is large, there is room for increasing the MCH level of SCCH. That is, when the SCCH multiplexing number is large, the SCCH communication overhead can be reduced by setting the SCCH MCS to an MCS with a high MCS level and increasing the transmission rate (bit rate).

  Therefore, in the present embodiment, the SCCH MCS, that is, the MCS in the encoding / modulation sections 101-1 to 101-n is set as follows. Hereinafter, an example of MCS setting by the MCS setting unit 120 will be shown.

  In the setting example according to the present embodiment, a case will be described in which the SCCH multiplexing number is fixed without changing for each subframe.

  In the following description, any MCS with MCS levels 1 to 8 as shown in FIG. 2 is set to SCCH. As is apparent from FIG. 2, the modulation level increases as the MCS level increases (the number of modulation multi-levels increases), and the encoding rate increases as the MCS level increases. That is, the higher the MCS level, the higher the transmission rate (bit rate), while the error rate characteristics deteriorate and the required transmission power for satisfying the predetermined error rate increases.

<MCS Setting Example 1-1 (FIGS. 3A and 3B)>
In this setting example, the MCS setting unit 120 includes the table shown in FIG. 3A and sets the SCCH MCS according to the number of multiplexed SCCHs. The number of multiplexed SCCHs is notified from a radio network controller (Radio Network Controller) in a layer higher than base station 100.

  According to this notification, the MCS setting unit 120 refers to the table shown in FIG. 3A and selects any one of the four MCSs. For example, when the SCCH multiplexing number is 3, an MCS with a modulation scheme: QPSK and a coding rate: R = 1/3 is selected and set in the encoding / modulation sections 101-1 to 101-n, and the SCCH When the multiplexing number is 9, MCS with modulation scheme: 16QAM and coding rate: R = 1/2 is selected and set in encoding / modulation sections 101-1 to 101-n. That is, MCS setting section 120 sets MCSs of a plurality of SCCHs multiplexed at the same time to MCSs having higher MCS levels as the number of SCCHs multiplexed increases. Further, the MCS setting unit 120 sets the MCSs of all SCCHs multiplexed at the same time to the same MCS.

  In this setting example, the table shown in FIG. 3B may be used instead of the table shown in FIG. 3A. The table shown in FIG. 3B is the same as the table shown in FIG. 3A in that the MCS level increases as the number of multiplexed SCCHs increases. However, in the table shown in FIG. 3B, the coding rate increases as the SCCH multiplexing number increases, but the modulation scheme is fixed to QPSK regardless of the SCCH multiplexing number.

  As described above, according to this setting example, the SCCH MCS is set in accordance with the number of multiplexed SCCHs, so that the SCCH transmission rate (bit rate) can be increased while satisfying the coverage target. Overhead can be reduced.

<MCS Setting Example 1-2 (FIGS. 4A and 4B)>
In general, as the system bandwidth increases, it becomes possible to accommodate more mobile stations. Therefore, it is considered that the number of mobile stations per subframe increases as the system bandwidth increases. That is, it is considered that the SCCH multiplexing number increases as the system bandwidth increases. Therefore, the same effect as in Setting Example 1-1 can be obtained by setting the SCCH MCS according to the system bandwidth instead of setting the SCCH according to the number of multiplexed SCCHs.

  Therefore, in the present setting example, the MCS setting unit 120 includes the table shown in FIG. 4A and sets the SCCH MCS according to the system bandwidth. The system bandwidth is notified from a radio network controller station in a layer higher than base station 100.

  According to this notification, the MCS setting unit 120 refers to the table shown in FIG. 4A and selects any one of the four MCSs. For example, when the system bandwidth is 5 MHz, an MCS with a modulation scheme: QPSK and a coding rate: R = 1/3 is selected and set in the encoding / modulation units 101-1 to 101-n, and the system bandwidth Is 20 MHz, MCS with modulation scheme: 16QAM and coding rate: R = 1/2 is selected and set in encoding / modulation sections 101-1 to 101-n. That is, the MCS setting unit 120 sets the MCSs of a plurality of SCCHs multiplexed at the same time to an MCS having a higher MCS level as the system bandwidth is wider. Further, the MCS setting unit 120 sets the MCSs of all SCCHs multiplexed at the same time to the same MCS.

  In this setting example, the table shown in FIG. 4B may be used instead of the table shown in FIG. 4A as in setting example 1-1.

As described above, according to the present setting example, the SCCH MCS is set according to the system bandwidth, so that the SCCH transmission rate (bit rate) can be increased while satisfying the coverage target as in the setting example 1-1. Therefore, the communication overhead by SCCH can be reduced.

<MCS Setting Example 1-3 (FIGS. 5A and 5B)>
Recently, multicast communication has been studied. Multicast communication is not one-to-one communication like unicast communication, but one-to-many communication. That is, in multicast communication, one base station transmits the same data to a plurality of mobile stations. With this multicast communication, music data and video image data distribution services, broadcast services such as television broadcasting, and the like are realized in the mobile communication system. On the other hand, in unicast communication, one base station transmits different data to a plurality of mobile stations.

  Recently, switching between multicast communication and unicast communication in units of subframes has been studied. Hereinafter, a subframe in which multicast communication is performed is referred to as a multicast subframe, and a subframe in which unicast communication is performed is referred to as a unicast subframe.

  Note that multicast communication is a communication mode in which information is transmitted only to a specific mobile station that subscribes to the service such as a newsgroup, whereas broadcast communication is all the same as current television broadcasting and radio broadcasting. The communication form is such that information is transmitted to the mobile station. However, multicast and broadcast are the same in that one base station transmits the same data to a plurality of mobile stations. Thus, multicast is sometimes referred to as broadcast. The multicast and broadcast may be collectively referred to as MBMS (Multimedia Broadcast / Multicast Service).

  In the multicast subframe, as described above, since individual data for each mobile station is not transmitted, there is no SCCH for the individual data. Therefore, the number of multiplexed SCCHs is smaller in the multicast subframe than in the unicast subframe. Therefore, instead of setting the SCCH MCS according to the number of multiplexed SCCHs, a setting example is also possible even if the subframe type is set according to whether the subframe is a multicast subframe or a unicast subframe. The same effect as 1-1 can be obtained.

  Therefore, in this setting example, the MCS setting unit 120 includes the table shown in FIG. 5A and sets the SCCH MCS according to the subframe type. The subframe type is notified from a radio network controller station in a layer higher than base station 100.

  In accordance with this notification, the MCS setting unit 120 refers to the table shown in FIG. 5A and selects one of the two MCSs. That is, when the subframe type is a multicast subframe, MCS with modulation scheme: QPSK and coding rate: R = 1/3 is selected and set in encoding / modulation sections 101-1 to 101-n, When the subframe type is a unicast subframe, an MCS with a modulation scheme: 16QAM and a coding rate: R = 1/2 is selected and set in the encoding / modulation sections 101-1 to 101-n. That is, the MCS setting unit 120 sets the MCS higher than the MCS level of the MCS set for the plurality of SCCHs multiplexed at the same time in the multicast subframe for the plurality of SCCHs multiplexed at the same time in the unicast subframe. Set the level MCS. Further, the MCS setting unit 120 sets the MCSs of all SCCHs multiplexed at the same time to the same MCS.

  In this setting example, the table shown in FIG. 5B may be used instead of the table shown in FIG. 5A as in setting example 1-1.

As described above, according to this setting example, the SCCH MCS is set according to the subframe type, so that the SCCH transmission rate (bit rate) can be increased while satisfying the coverage target as in setting example 1-1. Therefore, the communication overhead by SCCH can be reduced.

  The MCS setting examples 1-1 to 1-3 have been described above.

  Thus, according to the present embodiment, the SCCH MCS is set according to the SCCH multiplexing number, the system bandwidth, or the subframe type, so that the SCCH transmission rate (bit rate) is satisfied while satisfying the coverage target. ), And thus communication overhead due to SCCH can be reduced.

  Also, according to the present embodiment, base station 100 notifies SCCS MCS to all mobile stations by notifying all mobile stations of the SCCH multiplexing number, system bandwidth, or subframe type in common. Can be done. Therefore, according to the present embodiment, it is possible to omit the notification of each SCCS MCS mobile station, thereby further reducing the communication overhead due to SCCH.

(Embodiment 2)
In the first embodiment, the case has been described where the number of multiplexed SCCHs does not change for each subframe and is fixed. On the other hand, when the SCCH multiplexing number changes for each subframe, the configuration of the base station is as shown in FIG. In FIG. 6, the same components as those in FIG. 1 (Embodiment 1) are denoted by the same reference numerals, and description thereof is omitted.

  In base station 200 shown in FIG. 6, adaptive control section 115 determines the number of multiplexed SCCHs for each subframe in consideration of the number of mobile stations for each subframe in addition to the processing described in Embodiment 1. The determined SCCH multiplexing number is output to MCS setting section 120.

  MCS setting section 120 sets SCCH MCS according to the number of multiplexed SCCHs, as in MCS setting example 1-1 of the first embodiment.

  Thus, according to the present embodiment, even when the SCCH multiplexing number changes for each subframe, the SCCH MCS can be set to the optimum MCS according to the SCCH multiplexing number. Therefore, even when the SCCH multiplexing number changes for each subframe, the communication overhead due to SCCH can be reduced while satisfying the coverage target.

(Embodiment 3)
In the case where eight MCSs as shown in FIG. 2 can be set as SCCS MCSs, in order to notify each mobile station of the set MCSs, three of '000' to '111' respectively corresponding to the eight MCSs Bit information is required.

  Further, as described in the first embodiment, when the SCCH multiplexing number is small, it is necessary to set the MCS of the SCCH to the MCS having a low MCS level. On the other hand, when the number of multiplexed SCCHs is large, the MCS of the SCCH can be set to an MCS with a high MCS level.

  Therefore, in the present embodiment, the MCS that can be set in the SCCH is limited to some MCS candidates according to the number of multiplexed SCCHs, the system bandwidth, or the subframe type. The communication overhead by SCCH is reduced by reducing the number of bits.

FIG. 7 shows the configuration of base station 300 according to the present embodiment. In FIG. 7, the same components as those in FIG. 1 (Embodiment 1) are denoted by the same reference numerals, and description thereof is omitted.

  In base station 300 shown in FIG. 7, each decoding unit 32 outputs reception quality information of reception data obtained by decoding processing to transmission power control unit 103, adaptive control unit 115, and MCS setting unit 201.

  The MCS setting unit 201 sets the MCS in the encoding / modulation units 101-1 to 101-n. Hereinafter, an example of MCS setting by the MCS setting unit 201 will be described.

  In the setting example according to the present embodiment, a case will be described in which the SCCH multiplexing number is fixed without changing for each subframe.

<MCS Setting Example 2-1 (FIGS. 8A, 8B, 8C)>
In this setting example, the MCS setting unit 201 includes the table shown in FIG. 8A and limits the SCCH MCS candidates according to the number of multiplexed SCCHs. Also, the MCS setting unit 201 sets any one MCS among the limited MCS candidates to the SCCH according to the average reception quality of all mobile stations. The number of multiplexed SCCHs is reported from a radio network controller station in a layer higher than base station 300.

  The MCS setting unit 201 refers to the table shown in FIG. 8A according to this notification, and first limits to two MCS candidates among the eight MCSs shown in FIG. For example, when the number of multiplexed SCCHs is 3, there are two modulation schemes: QPSK, coding rate: R = 1/4 MCS, and modulation scheme: QPSK, coding rate: R = 1/3 MCS. MCS is an MCS candidate for SCCH. When the SCCH multiplexing number is 9, there are two modulation schemes: 16QAM, coding rate: MCS with R = 1/2, and modulation scheme: 16QAM, coding rate: MCS with R = 3/4. MCS is an MCS candidate for SCCH. That is, the MCS setting unit 201 limits MCS candidates of a plurality of SCCHs multiplexed at the same time to MCSs having higher MCS levels as the SCCH multiplexing number increases.

  As a result, in order to notify each mobile station of the set MCS, 1-bit information of '0' or '1' corresponding to two MCS candidates is sufficient.

  Next, the MCS setting unit 201 compares the average reception quality of all the mobile stations obtained from the reception quality information input from each decoding unit 32 with a threshold value, and compares the result with reference to the table shown in FIG. 8A. In response, one of the two MCS candidates is selected. For example, when the SCCH multiplexing number is 3 and the average reception quality is less than the threshold value TH2, the MCS with the modulation scheme: QPSK and the coding rate: R = 1/4 is selected, and the encoding / modulating section 101 -1 to 101-n. On the other hand, when the SCCH multiplexing number is 3 and the average reception quality is equal to or higher than the threshold value TH2, the MCS with the modulation scheme: QPSK and the coding rate: R = 1/3 is selected and the encoding / modulating section 101 is selected. -1 to 101-n. Further, the MCS setting unit 201 sets the MCSs of all SCCHs multiplexed at the same time to the same MCS.

  The relationship between the threshold values in FIG. 8A is TH1 <TH2 <TH3 <TH4.

In this setting example, the table shown in FIG. 8B may be used instead of the table shown in FIG. 8A. The table shown in FIG. 8B is the same as the table shown in FIG. 8A in that the maximum MCS level of MCS candidates becomes higher as the SCCH multiplexing number increases. However, in the table shown in FIG. 8B, some MCS candidates overlap between the divisions of the SCCH multiplexing number. For example, an MCS with modulation scheme: QPSK and coding rate: R = 1/4 becomes both MCS candidates when the SCCH multiplexing number is 3 or 4 and when the SCCH multiplexing number is 5-8.

  In this setting example, the table shown in FIG. 8C may be used instead of the table shown in FIG. 8A. The table shown in FIG. 8C is the same as the table shown in FIG. 8A in that the maximum MCS level of MCS candidates increases as the number of multiplexed SCCHs increases. However, in the table shown in FIG. 8C, between the divisions of the SCCH multiplexing number, the maximum MCS level of the MCS candidate in one division is between the maximum MCS level and the minimum MCS level of the MCS candidate in the other division. is there. For example, the modulation scheme: QPSK when the SCCH multiplexing number is 3, 4 and the coding rate: MCS level of the MCS candidate with R = 1/3 (the maximum MCS level when the SCCH multiplexing number is 3, 4) is Modulation method when SCCH multiplexing number is 5-8: QPSK, coding rate: MCS level of MCS candidate with R = 1/2 (maximum MCS level when SCCH multiplexing number is 5-8) and SCCH Modulation method when multiplex number is 5-8: between QPSK and coding rate: MCS level of MCS candidate with R = 1/4 (minimum MCS level when SCCH multiplex number is 5-8) is there.

  As described above, according to this setting example, the SCCH MCS candidates are limited according to the number of multiplexed SCCHs, so that the SCCH transmission rate (bit rate) can be increased while satisfying the coverage target as in the first embodiment. Therefore, the communication overhead by SCCH can be reduced.

  Also, according to this setting example, the signaling amount can be reduced by reducing the number of bits necessary for the information for notifying the mobile station of the SCCH MCS, thereby further reducing the SCCH communication overhead. it can.

  Further, since the MCS is set using the reception quality, it is possible to set an MCS more accurate than that in the first embodiment.

<MCS Setting Example 2-2 (FIGS. 9A, 9B, and 9C)>
In this setting example, the MCS setting unit 201 includes the table shown in FIG. 9A and limits SCCH MCS candidates according to the number of multiplexed SCCHs in the same manner as in Setting Example 2-1. Also, the MCS setting unit 201 sets any one MCS among limited MCS candidates for each SCCH according to the reception quality for each mobile station. The number of multiplexed SCCHs is reported from a radio network controller station in a layer higher than base station 300. The limitation of the MCS candidates in this setting example is the same as that in setting example 2-1, and thus the description thereof is omitted.

  Based on the reception quality of each mobile station obtained from the reception quality information input from each decoding unit 32, the MCS setting unit 201 assigns each mobile station a first group with a low reception quality and a second group with a high reception quality. Classify into: Then, the MCS setting unit 201 selects one MCS from two MCS candidates for each SCCH with reference to the table shown in FIG. 9A. For example, when the SCCH multiplexing number is 3, the MCS with the modulation scheme: QPSK and the coding rate: R = 1/4 is selected for the SCCH of the mobile station belonging to the first group, and the coding / modulation is performed. Of the units 101-1 to 101-n, the encoding / modulation unit corresponding to the mobile station is set. On the other hand, when the SCCH multiplexing number is 3, the MCS with the modulation scheme: QPSK and the coding rate: R = 1/3 is selected for the SCCH of the mobile station belonging to the second group, and the coding / modulation is performed. Of the units 101-1 to 101-n, the encoding / modulation unit corresponding to the mobile station is set.

  In this setting example, as in setting example 2-1, the table shown in FIG. 9B or the table shown in FIG. 9C may be used instead of the table shown in FIG. 9A.

Thus, according to this setting example, the SCCH MCS candidates are assigned to the SCCH as in Setting Example 2-1.
Therefore, the SCCH transmission rate (bit rate) can be increased while satisfying the coverage target, and thus the communication overhead by the SCCH can be reduced.

  Further, according to the present setting example, as in setting example 2-1, since the number of bits necessary for information for notifying the mobile station of SCCH MCS can be reduced, the amount of signaling can be reduced. The overhead can be further reduced.

  Further, since the MCS is set for each SCCH using the reception quality for each mobile station, it is possible to set a more accurate MCS than the setting example 2-1.

  The MCS setting examples 2-1 and 2-2 have been described above.

  In the setting examples 2-1 and 2-2, the MCS candidates are limited in accordance with the number of multiplexed SCCHs. However, in accordance with the setting example 1-2 and the setting example 1-3 in the first embodiment, the system bandwidth or The MCS candidates may be limited according to the subframe type.

  Further, the MCS setting unit 201 has a plurality of tables in which different MCS candidates are set according to the SCCH multiplexing number, system bandwidth, or subframe type, and the SCCH multiplexing number, system bandwidth, or The MCS candidates may be limited by selecting any one table according to the subframe type.

  Thus, according to the present embodiment, the SCCH MCS candidates are set according to the SCCH multiplexing number, system bandwidth, or subframe type, so that the coverage target is satisfied as in the first embodiment. The transmission rate (bit rate) of SCCH can be increased, and thus communication overhead by SCCH can be reduced.

(Embodiment 4)
In the third embodiment, a case has been described in which the SCCH multiplexing number is fixed without changing for each subframe. On the other hand, when the SCCH multiplexing number changes for each subframe, the configuration of the base station is as shown in FIG. In FIG. 10, the same components as those in FIG. 7 (Embodiment 3) are denoted by the same reference numerals, and the description thereof is omitted.

  In base station 400 shown in FIG. 10, adaptive control section 115 determines the SCCH multiplexing number in consideration of the number of mobile stations and the like in addition to the processing described in Embodiment 3, and uses the determined SCCH multiplexing number as MCS setting section. To 201.

  MCS setting section 201 limits SCCH MCS candidates according to the number of multiplexed SCCHs in the same manner as MCS setting example 2-1 and MCS setting example 2-2 of the third embodiment.

  As described above, according to the present embodiment, even when the SCCH multiplexing number changes for each subframe, the SCCH MCS candidates can be limited to the optimum MCS candidates according to the SCCH multiplexing number. Therefore, even when the SCCH multiplexing number changes for each subframe, the communication overhead due to SCCH can be reduced while satisfying the coverage target.

  The embodiment of the present invention has been described above.

  The subframe used in the above description may be another transmission time unit such as a time slot or a frame.

  Further, the resource block used in the above description may be another transmission unit in the frequency domain such as a subcarrier block.

  Also, the mobile station may be referred to as UE, the base station apparatus as Node B, and the subcarrier as tone. A resource block may also be referred to as a subband, a subchannel, a subcarrier block, or a chunk. The CP may also be referred to as a guard interval (GI).

In addition, the SCCH may transmit control signals such as uplink allocation information, Ack / Nack signal, PI (Paging Indicator), random access response, etc., in addition to the mobile station ID, resource block number, and MCS information. SCCH is a PDCCH (Physical Dowlink Control).
CHannel).

  In the above description, SCCH is given as an example of a channel that is multiplexed at the same time and whose transmission power is individually controlled for each mobile station. However, the present invention is not limited to this, and the present invention can be applied to all channels that are multiplexed at the same time and individually transmitted for each mobile station.

  In the above description, control information for one mobile station is transmitted on one SCCH. However, a plurality of mobile stations may be grouped and one SCCH may be used for each group. In this case, transmission power control based on reception quality is performed in accordance with the mobile station having the lowest reception quality in the group.

  In the above description, the example in which the SCCH is arranged at the head of the subframe has been described. However, the SCCH may be arranged at a position other than the head of the subframe, for example, the second OFDM symbol of the subframe. Good.

  In the above description, the example in which the SCCH and the data channel are time-multiplexed has been described. However, the SCCH and the data channel may be frequency-multiplexed.

  Further, the SCCH multiplexing method is not limited to frequency multiplexing, and may be code multiplexing, for example.

  In the above description, the transmission power control is performed after the SCCH is allocated to each subcarrier. However, the transmission power control may be performed to each subcarrier after performing the transmission power control for the SCCH. That is, in FIGS. 1, 6, 7, and 10, the positions of the placement unit 102 and the transmission power control unit 103 may be interchanged, and the transmission power control unit 103 may be provided in the previous stage of the placement unit 102.

  Further, the method for performing the conversion between the frequency domain and the time domain is not limited to IFFT and FFT.

  Further, the higher the MCS level, the smaller the amount of resources used. Therefore, the amount of resources (time, frequency, antenna) used for the SCCH may be changed according to the SCCS MCS level. For example, when the MCS level is increased as the number of multiplexed SCCHs is increased as in the MCS setting example 1-1 of the first embodiment, the resource amount used for one SCCH is increased as the number of multiplexed SCCHs is increased. Less is better.

Further, the present invention may be applied to only some of the plurality of SCCHs multiplexed in one subframe. For example, among a plurality of SCCHs multiplexed in one subframe, MCS (for example, modulation scheme: QPSK) that can obtain a required reception quality in a mobile station near a cell boundary without increasing transmission power for one SCCH. , Coding rate: R = 1/8), and for other SCCHs, an MCS corresponding to the number of multiplexed SCCHs may be set.

  Further, although cases have been described with the above embodiment as examples where the present invention is configured by hardware, the present invention can also be realized by software.

  Each functional block used in the description of the above embodiment is typically realized as an LSI which is an integrated circuit. These may be individually made into one chip, or may be made into one chip so as to include a part or all of them. The name used here is LSI, but it may also be called IC, system LSI, super LSI, or ultra LSI depending on the degree of integration.

  Further, the method of circuit integration is not limited to LSI's, and implementation using dedicated circuitry or general purpose processors is also possible. An FPGA (Field Programmable Gate Array) that can be programmed after manufacturing the LSI, or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used.

  Furthermore, if integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology. Biotechnology can be applied.

  The disclosure of the specification, drawings, and abstract contained in the Japanese application of Japanese Patent Application No. 2006-349785 filed on Dec. 26, 2006 is incorporated herein by reference.

  The present invention can be applied to a mobile communication system or the like.

FIG. 3 is a block diagram showing a configuration of a base station according to the first embodiment. The figure which shows the MCS level which concerns on Embodiment 1. Reference table according to MCS setting example 1-1 of the first embodiment (table example 1) Reference table according to MCS setting example 1-1 of the first embodiment (table example 2) Reference table according to MCS setting example 1-2 of the first embodiment (table example 1) Reference table according to MCS setting example 1-2 of the first embodiment (table example 2) Reference table according to MCS setting example 1-3 of the first embodiment (table example 1) Reference table according to MCS setting example 1-3 of the first embodiment (table example 2) Block diagram showing the configuration of a base station according to Embodiment 2 FIG. 9 is a block diagram showing a configuration of a base station according to Embodiment 3 Reference table according to MCS setting example 2-1 of the third embodiment (table example 1) Reference table according to MCS setting example 2-1 of the third embodiment (table example 2) Reference table according to MCS setting example 2-1 of the third embodiment (table example 3) Reference table according to MCS setting example 2-2 of the third embodiment (table example 1) Reference table according to MCS setting example 2-2 of the third embodiment (table example 2) Reference table according to MCS setting example 2-2 of the third embodiment (table example 3) Block diagram showing a configuration of a base station according to Embodiment 4

Claims (3)

In a system bandwidth in which a plurality of control channels for a plurality of mobile stations are arranged , the radio communication base station apparatus multiplexes the plurality of control channels at the same time,
Encoding means for encoding the plurality of control channels;
Modulation means for modulating the plurality of control channels;
The MCS in the encoding means and the modulating means, as the system bandwidth is wide, a setting unit MCS level is set to a higher MCS,
A wireless communication base station apparatus comprising: The setting means sets the MCS having a higher MCS level as the number of multiplexed control channels increases.
The radio communication base station apparatus according to claim 1. In a system bandwidth in which a plurality of control channels for a plurality of mobile stations are arranged, the control channel MCS control method in a radio communication base station device that multiplexes the plurality of control channels at the same time
The MCS of the control channel, the higher the system bandwidth is wide, MCS level is set to a higher MCS,
MCS control method.

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